The word "chute" could be used to mean either the spinnaker, or the tunnel under the foredeck. I'm assuming in this case though Roy is referring to the tunnel. Does enlarging the throat require any modification of the forestay stem plate? In the link DK provided above, it appears that no such modification was required. Might be a different story for boats with furlers. My old Rondar has a furler with the drum above the deck. On some older 5O5's with furlers, the drum is below the deck. If your Kyrwood has this feature enlarging the throat without modifying the forestay might be difficult.